1. Field of the Invention
The present invention relates to a propelling apparatus for a lawn tractor for selectively providing a two-wheel drive mode and a four-wheel drive mode.
2. Description of the Related Art
A front-mount lawn tractor, as shown in Japanese Utility Model Publication Kokai No. 4-71305, has dirigible rear wheels which can also be driven to run in a four-wheel drive mode. This provides an improved performance for running in adverse ground conditions or for running on uphill grounds. With an ordinary four-wheel drive structure, front and rear wheels are driven at different rates when making a turn. When making a small, sharp turn, the wheels tend to slip and damage lawn. Where protection of lawn is a primary consideration, a two-wheel drive structure is often employed to avoid slippage during a small, sharp turn although its running performance on uphill grounds may not be satisfactory.
Lawn tractors are used widely in parks and on golf courses. Such tractors are driven by many people in many different ways. There are persistent demands among those people for four-wheel drive tractors having a strong driving force effective for grass cutting operations on uneven grounds.
However, simply employing a conventional four-wheel drive structure would again pose the problem of slippage during a small, sharp turn. It is necessary to develop and equip a four-wheel drive structure that overcomes the above disadvantage (e.g. a transmission mechanism or a center differential whose drive speed is variable with a turning radius). However, such a structure is complicated and expensive.